Active power factor correction (APFC) is an important way to utilize energy in an efficient and low-pollution way. In APFC approaches, a power converter may be added between a bridge rectifier and an output capacitor filter, such that the power factor is close to 1. An APFC circuit can operate at a relatively high frequency switching state with characteristics of relatively small size, light weight, and high efficiency. Because of these characteristics, APFC has increasingly become a focus of power electronics technology research.